1. Field of the Invention
The present invention relates to a nitride semiconductor light emitting device suitably applied to a light emitting device such as a light emitting diode (LED) or a laser diode (LD), as well as to a method of manufacturing the same.
2. Description of the Background Art
When a light emitting diode (LED) is used as an illuminating light source or a backlight for a display, it is necessary that the device has high light emitting efficiency and low forward voltage (hereinafter denoted as Vf). Japanese Patent Laying-Open No. 2000-244072 proposes a technique for improving light emission output of an LED, by forming an n-side first multi-layered film layer having at least two pairs of two different types of nitride semiconductor layers, that is, a nitride semiconductor layer doped with an n-type impurity and an undoped nitride semiconductor layer not doped with the n-type impurity. Further, Japanese Patent Laying-Open No. 2000-244072 describes that Vf is lowered by providing an n-side second multi-layered film layer, formed by stacking a first nitride semiconductor layer containing In and a second nitride semiconductor layer having a composition different from the first nitride semiconductor layer, between the n-side first multi-layered film layer and an active layer.
It is noted, however, that the n-type contact layer is formed by selecting at least one of the method involving increased carrier density and a method involving smaller band gap, in order to decrease contact resistance to lower Vf. Therefore, the layer tends to contain much dislocation and defects. When the n-side first multi-layered film layer is stacked in contact with the n-type contact layer, it would undesirably be influenced by the dislocation or defects, and sufficient effect of improving light emission output would not be attained. Further, in Japanese Patent Laying-Open No. 2000-244072, the second multi-layered film layer is stacked to the side of the active layer than the n-side first multi-layered film layer. When two different types of multi-layered films are grown, manufacturing process becomes complicated and the manufacturing cost increases. In addition, stacking of a nitride semiconductor layer containing In on the n-side of the active layer induces dislocation and defects of In, which affects crystallinity of the active layer and possibly causes decrease in light emission output.